Coal gangue treatment and processing technological method

Abstract

The invention relates to the field of solid waste resource utilization, in particular to a coal gangue treatment and processing technological method. The coal gangue treatment and processing technological method comprises the following steps: crushing and grinding coal gangue in sequence to obtain coal gangue powder; the coal gangue powder is subjected to first calcination, and calcined coal gangue is obtained; mixing the calcined coal gangue with a nitric acid solution, and carrying out oxidation treatment to obtain a precipitate; mixing the precipitate, a chemical activator and a solvent, carrying out heat treatment, and carrying out solid-liquid separation to obtain filter residues and filtrate; carrying out secondary calcination on the filter residue to obtain a silicon fertilizer; and adding an acidic leaching solution into the filtrate to adjust the pH value to be acidic, thereby obtaining the humic acid. According to the invention, inorganic matters in the coal gangue are prepared into the silicon fertilizer, and organic matters are prepared into the humic acid, so that combined preparation of the silicon fertilizer and the humic acid is realized, the production cost is greatly reduced, and high value-added utilization of solid wastes is realized.

Description

A coal gangue processing technology Technical Field

[0001] This invention relates to the field of solid waste resource utilization, and in particular to a process for treating and processing coal gangue. Background Technology

[0002] Coal gangue is a waste product generated during coal mining, washing, and processing, and is a typical large-scale industrial solid waste. The amount of coal gangue produced is approximately 10% to 25% of coal mining output. Large-scale accumulation of coal gangue not only occupies land resources but also easily ignites, causing fires and producing harmful gases that pollute the atmosphere. With increasing weathering, heavy metals and harmful substances in coal gangue continuously migrate downstream, causing pollution problems such as excessive heavy metal levels and the accumulation of harmful substances in the mining area soil. Therefore, expanding the resource utilization pathways of coal gangue, improving its comprehensive utilization rate, and achieving large-scale disposal are urgently needed.

[0003] Coal gangue is similar to soil in elemental and mineral composition, and its high silicon content makes it a potential source of citric acid-soluble silicon fertilizer. Silicon fertilizer has a beneficial effect on improving the soil ecology of saline-alkali land, helping to retain water, fertilize the soil, and mitigate soil erosion. Since coal mines are mainly located near saline-alkali land, preparing coal gangue-based silicon fertilizer for saline-alkali land remediation not only saves transportation costs and allows for localized solid waste treatment but also embodies the green development approach of treating waste with waste. However, silicon in coal gangue is mostly present in the form of quartz, which plants cannot directly absorb. Therefore, to prepare high-efficiency organosilicon fertilizer, coal gangue must be modified to transform the silicon-containing compounds into available silicon that can be absorbed by plants. Humic acid has a wide range of applications in agriculture. It can be used to prepare soil conditioners, pesticide compounding agents, organic fertilizers, etc. Coal gangue also contains a certain amount of humic acid. If humic acid can be extracted simultaneously during the preparation of silicon fertilizer, the multi-level utilization of solid waste can be maximized, thereby improving the overall economic benefits.

[0004] Most current methods focus only on the activation of silicon or the separate extraction of humic acid, making it difficult to achieve the synergistic preparation of two high-value products in the same process system. Furthermore, they often suffer from problems such as complex processes, high energy consumption, or unsatisfactory product purity. Summary of the Invention

[0005] This invention provides a coal gangue processing method, silicon fertilizer, humic acid, and their applications, addressing the problems of large-scale coal gangue accumulation and limited resource utilization pathways. It employs a three-stage activation process—mechanical activation, chemical activation, and thermal activation—to modify silicon-containing compounds in the coal gangue. Different chemical activators are used at high temperatures to alter the form of silicon in the coal gangue, increasing the effective silicon content in the fertilizer and improving its quality. The separation of filter residue and filtrate enables the joint production of silicon fertilizer and humic acid, reducing secondary pollution.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution: The present invention provides a coal gangue processing method, comprising the following steps: sequentially crushing and grinding the coal gangue to obtain coal gangue powder; subjecting the coal gangue powder to a first calcination to obtain calcined coal gangue; mixing the calcined coal gangue with nitric acid solution and performing oxidation treatment to obtain a precipitate; mixing the precipitate, a chemical activator, and a solvent, performing heat treatment, and after solid-liquid separation, obtaining filter residue and filtrate; subjecting the filter residue to a second calcination to obtain silicon fertilizer; adding an acidic extract to the filtrate to adjust the pH value to acidic to obtain humic acid.

[0007] In some specific embodiments, the particle size of the coal gangue powder is 0.074~0.3mm.

[0008] In some specific embodiments, the temperature of the first calcination is 600~800℃, and the time of the first calcination is 0.5~1.5h.

[0009] In some specific embodiments, the first calcination is carried out under aerobic conditions.

[0010] In some specific embodiments, the ratio of the calcined coal gangue to the nitric acid solution is (2~8) g: 1 mL.

[0011] In some specific embodiments, the concentration of the nitric acid solution is 5wt%~20wt%; in some specific embodiments, the oxidation treatment temperature is 10~30℃, and the oxidation treatment time is 1~4h.

[0012] In some specific embodiments, the mass ratio of the calcined coal gangue to the chemical activator is 1 to 10:1.

[0013] In some specific embodiments, the ratio of the chemical activator to the solvent is 1 g: (5~35) mL.

[0014] In some specific embodiments, the chemical activator includes one or two of nitrates, sulfates, carbonates, and chlorides.

[0015] In some specific embodiments, the nitrate includes at least one of calcium nitrate, magnesium nitrate, and potassium nitrate.

[0016] In some specific embodiments, the sulfate includes at least one of calcium sulfate, magnesium sulfate, and potassium sulfate.

[0017] In some specific embodiments, the carbonate includes at least one of calcium carbonate, magnesium carbonate, and potassium carbonate.

[0018] In some embodiments, the chloride salt includes at least one of calcium chloride, magnesium chloride, and potassium chloride. In some embodiments, the solvent includes water.

[0019] In some specific embodiments, the heat treatment includes microwave heat treatment; the conditions for microwave heat treatment are: power of 200~900W, temperature of 30~90℃, and time of 20~60min.

[0020] In some specific embodiments, the temperature of the second calcination is 700~1100℃ and the temperature of the second calcination is higher than that of the first calcination, and the time of the second calcination is 2~6h.

[0021] In some specific embodiments, the acidic extract includes a sulfuric acid solution or hydrochloric acid.

[0022] In some specific embodiments, the concentration of the acidic extract is 10wt% to 20wt%.

[0023] In some specific implementations, the target pH value is 1.2 to 1.9.

[0024] Compared with the prior art, the present invention has the following beneficial effects: The coal gangue processing method of the present invention first crushes and grinds the coal gangue (mechanical activation) to obtain coal gangue powder. After primary calcination of the coal gangue powder, it is mixed with nitric acid solution and subjected to oxidation treatment to obtain precipitate. The precipitate is mixed with a chemical activator and subjected to heat treatment (chemical activation) to obtain filter residue and filtrate. The filter residue is calcined (thermal activation) to obtain silicon fertilizer. The pH value of the filtrate is adjusted to acidic to obtain humic acid. This invention modifies silicon-containing compounds in coal gangue through a three-stage activation process involving mechanical activation, chemical activation, and thermal activation. This significantly increases the effective silicon content. The chemical activation process incorporates a large amount of activating agent, which not only promotes the efficient conversion of effective silicon during subsequent thermal activation but also provides conditions for the subsequent extraction of humic acid. Furthermore, the use of nitric acid to treat the calcined coal gangue effectively removes some impurities and ash from the surface pores, improving the quality of the silicon fertilizer. Nitric acid also has strong oxidizing properties; the nitro, nitroso, and oxygen it provides oxidize and degrade large organic molecules, breaking active bonds and increasing the extraction yield of humic acid. In addition, the nitric acid pretreatment after high-temperature calcination removes a large amount of aluminum from the coal gangue, greatly reducing the harmful effects of aluminum in the fertilizer on the soil and crops.

[0025] This invention enables the combined production of silicon fertilizer and humic acid. Inorganic materials from coal gangue are prepared into silicon fertilizer, and organic materials are prepared into humic acid. The same technical route is used to prepare two high-value-added products, which greatly reduces production costs and realizes the high-value-added utilization of solid waste. Detailed Implementation

[0026] The present invention will be described below through specific embodiments. Those skilled in the art will understand that the specific embodiments described below are for illustrative purposes only and do not limit the scope of the invention in any way. Furthermore, in the following embodiments, unless otherwise specified, the reagents and equipment used are commercially available. If specific processing conditions and methods are not explicitly described in the following embodiments, conditions and methods known in the art can be used for processing.

[0027] This invention provides a processing method for coal gangue, comprising the following steps: sequentially crushing and grinding the coal gangue to obtain coal gangue powder; subjecting the coal gangue powder to a first calcination to obtain calcined coal gangue; mixing the calcined coal gangue with a nitric acid solution and performing an oxidation treatment to obtain a precipitate; mixing the precipitate with a chemical activator and a solvent and performing a heat treatment, followed by solid-liquid separation to obtain filter residue and filtrate; subjecting the filter residue to a second calcination to obtain silicon fertilizer; and adding an acidic extract to the filtrate to adjust the pH value to acidic to obtain humic acid.

[0028] The coal gangue processing method of this invention first involves crushing and grinding the coal gangue (mechanical activation) to obtain coal gangue powder. The coal gangue powder is then subjected to primary calcination and mixed with nitric acid solution for oxidation treatment, resulting in a precipitate. The precipitate is then mixed with a chemical activator and subjected to heat treatment (chemical activation) to obtain filter residue and filtrate. The filter residue is calcined (thermal activation) to obtain silicon fertilizer. The pH of the filtrate is adjusted to acidity to obtain humic acid. Firstly, the physical crushing process increases the reaction surface area of ​​the coal gangue, destroys some of the crystal structure, and reduces crystallinity, providing a sufficient interface and higher reactivity for subsequent chemical reactions. Then, during the first calcination process, crystal water and volatile organic compounds are removed, causing a phase transition in the clay minerals, reducing their structural stability, making them more susceptible to attack during subsequent nitric acid oxidation, and simultaneously generating highly active amorphous alumina, creating the material conditions for selective dealumination reactions. Subsequently, nitric acid solution is used for oxidation treatment to dissolve the basic / ampholy oxides in the calcination product. Furthermore, the highly active amorphous alumina produced in the primary calcination reacts with nitric acid, selectively leaching aluminum, which was originally firmly bonded to silicon via Si-O-Al bonds, into the solution. This causes the silicate mineral framework to collapse and loosen, forming a porous amorphous silica network rich in Si-OH groups. This creates structural conditions for subsequent silicon activation. The strong oxidizing properties of nitric acid also allow for the oxidative degradation of macromolecular organic matter in coal gangue into humic acids, laying the foundation for subsequent humic acid extraction. Then, a chemical activator is used to simultaneously activate and separate silicon and humic acid. Finally, a second calcination converts soluble silicon in the filter residue into citrate-soluble silicon, removing residual organic matter and ultimately shaping the silicon fertilizer product. Under acidic conditions, soluble humate salts are converted into precipitates, yielding the humic acid product.

[0029] In some embodiments, the particle size of the coal gangue powder is 0.074~0.3 mm. As an example, the particle size of the coal gangue powder can be 0.074 mm, 0.08 mm, 0.09 mm, 0.1 mm, 0.2 mm, and 0.3 mm, etc.

[0030] In this invention, the smaller particle size allows the reagent to have more opportunities to contact the active sites on the surface of the coal gangue particles, resulting in more efficient and uniform heat transfer, and more complete reactions such as dehydroxylation and organic pyrolysis. + and NO3 - Ions can penetrate into the pores of particles more quickly and deeply, dramatically increasing the efficiency of dissolving metal oxides. If the particles are too fine, the slurry viscosity will be higher, the filtration resistance will be greater, and the moisture content of the filter cake may also be higher. By controlling the particle size of the coal gangue powder within the above-mentioned range, both the reaction rate and extraction rate can be guaranteed, without making solid-liquid separation and product shaping too difficult.

[0031] In some embodiments, the temperature of the first calcination is 600~800℃, and the time of the first calcination is 0.5~1.5h. As an example, the temperature of the first calcination can be 600℃, 650℃, 680℃, 700℃, 720℃, 750℃, 780℃, and 800℃, etc., and the time of the first calcination can be 0.5h, 0.75h, 1h, 1.25h, and 1.5h, etc.

[0032] In this invention, the first calcination transforms kaolinite into highly active amorphous metakaolinite, while simultaneously and gently pyrolyzes organic matter to form pores and retain the active framework. If the temperature is too low, activation is insufficient, resulting in a low extraction rate; if the temperature is too high, inert crystalline phases such as mullite will be generated, deactivating the material, and the complete combustion of organic matter will lead to a zero extraction rate.

[0033] In some embodiments, the first calcination is carried out under aerobic conditions.

[0034] In some embodiments, the ratio of the calcined coal gangue to the nitric acid solution is (2~8) g:1 mL. As an example, the ratio of the calcined coal gangue to the nitric acid solution can be 2 g:1 mL, 3 g:1 mL, 4 g:1 mL, 5 g:1 mL, 6 g:1 mL, 7 g:1 mL, and 8 g:1 mL, etc.

[0035] In some embodiments, the concentration of the nitric acid solution is 5 wt% to 20 wt%. As an example, the concentration of the nitric acid solution can be 5 wt%, 8 wt%, 9 wt%, 10 wt%, 12 wt%, 13 wt%, 15 wt%, 18 wt%, and 20 wt%, etc.

[0036] In some embodiments, the oxidation treatment temperature is 10~30℃, and the oxidation treatment time is 1~4h. As examples, the oxidation treatment temperature can be 10℃, 12℃, 15℃, 17℃, 20℃, 22℃, 25℃, 28℃, and 30℃, etc., and the oxidation treatment time can be 1h, 1.5h, 2h, 2.5h, 3h, 3.5h, and 4h, etc.

[0037] In this invention, the parameters in the oxidation process directly affect the efficiency and depth of silicon-aluminum separation and organic matter degradation. The ratio of calcined coal gangue to the nitric acid solution determines the concentration of the reaction system; too low a concentration results in insufficient mass transfer, while too high a concentration wastes acid and increases the burden on subsequent processing. The nitric acid concentration is critical; too low a concentration results in insufficient aluminum removal oxidation, while too high a concentration may excessively damage the silicon framework and generate excessive nitrogen oxides. Temperature and time jointly control the reaction kinetics; low temperatures and short reaction times lead to incomplete reactions, while high temperatures and long reaction times, although improving efficiency, may promote silica gel formation or increase side reactions, and increase energy consumption and control costs. The goal of optimizing these parameters is to achieve efficient aluminum dissolution and effective oxidative degradation of organic matter while maximizing the preservation of the silicon framework structure and creating optimal conditions for subsequent alkaline extraction.

[0038] In some embodiments, after the oxidation treatment is completed, a post-treatment is further included, which includes: filtering the suspension obtained after the oxidation treatment to obtain a filter cake, washing the filter cake with water until the pH is neutral, and then drying it to remove moisture.

[0039] In some embodiments, the mass ratio of the calcined coal gangue to the chemical activator is 1 to 10:1. As an example, the mass ratio of the calcined coal gangue to the chemical activator can be 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, and 10:1, etc.

[0040] In this invention, the mass ratio of calcined coal gangue to chemical activator directly affects the silicon extraction rate and cost control. Within the aforementioned range, sufficient activator can efficiently dissolve amorphous silicon and extract humic acid, while avoiding waste caused by excessive reagents. If the ratio is too small (too much activator), although the reaction is sufficient, it will significantly increase reagent costs, subsequent neutralization burden, and product impurities; if the ratio is too large (too little activator), it will be unable to effectively depolymerize the silicon framework and extract humic acid, resulting in low silicon fertilizer yield and incomplete humic acid extraction.

[0041] In some embodiments, the ratio of the chemical activator to the solvent is 1 g: (5~35) mL. As an example, the ratio of the chemical activator to the solvent can be 1 g: 5 mL, 1 g: 10 mL, 1 g: 15 mL, 1 g: 20 mL, 1 g: 25 mL, 1 g: 30 mL, and 1 g: 35 mL, etc.

[0042] In some embodiments, the chemical activator includes, but is not limited to, one or two of nitrates, sulfates, carbonates, and chlorides.

[0043] In this invention, when the chemical activator is composed of any two of nitrates, sulfates, carbonates, and chlorides, the mass ratio of any two of the nitrates, sulfates, carbonates, and chlorides is (1~5):(1~5). As examples, the mass ratio of any two of the nitrates, sulfates, carbonates, and chlorides can be 1:1, 2:1, 3:1, 4:1, 5:1, 5:2, 5:3, and 5:4, etc.

[0044] In some embodiments, the nitrate includes, but is not limited to, at least one of calcium nitrate, magnesium nitrate, and potassium nitrate.

[0045] In some embodiments, the sulfate includes, but is not limited to, at least one of calcium sulfate, magnesium sulfate, and potassium sulfate.

[0046] In some embodiments, the carbonate includes, but is not limited to, at least one of calcium carbonate, magnesium carbonate, and potassium carbonate.

[0047] In some embodiments, the chloride salt includes, but is not limited to, at least one of calcium chloride, magnesium chloride, and potassium chloride. In some embodiments, the solvent includes, but is not limited to, water.

[0048] In some embodiments, the heat treatment includes microwave heat treatment; the conditions for the microwave heat treatment are: power of 200~900W, temperature of 30~90℃, and time of 20~60min. As an example, the power can be 200W, 300W, 400W, 500W, 600W, 700W, 800W, and 900W, the temperature can be 30℃, 40℃, 50℃, 60℃, 70℃, 80℃, and 90℃, and the time can be 20min, 25min, 30min, 35min, 40min, 45min, 50min, 55min, and 60min, etc.

[0049] In some embodiments, microwave heat treatment is performed while stirring, wherein the stirring speed is 300~900 r / min. As an example, the stirring speed can be 300 r / min, 400 r / min, 500 r / min, 600 r / min, 700 r / min, 800 r / min, and 900 r / min, etc.

[0050] In this invention, microwave heating is used to treat coal gangue suspension to achieve rapid modification treatment, which improves the activation effect and saves processing time.

[0051] In this invention, the method of solid-liquid separation is not specifically limited, and those skilled in the art can use conventional solid-liquid separation methods. In some embodiments, the solid-liquid separation method is centrifugation, the centrifugation speed is 2000 rpm, and the centrifugation time is 5-10 min.

[0052] In some embodiments, the temperature of the second calcination is 700~1100℃ and is higher than the temperature of the first calcination, and the time of the second calcination is 2~6h. As an example, the temperature of the second calcination can be 700℃, 750℃, 800℃, 850℃, 900℃, 950℃, 1000℃, 1050℃ and 1100℃, etc., and the time of the second calcination can be 2h, 2.5h, 3h, 3.5h, 4h, 4.5h, 5h, 5.5h and 6h, etc.

[0053] In this invention, the core of the first calcination is gentle activation, generating highly active amorphous metakaolinite through dehydroxylation; excessively high temperatures will lead to deactivation. The core of the second calcination is the synthesis reaction. To promote the formation of citrate-soluble silicates and create a slow-release silicon fertilizer, sufficient energy needs to be provided at a higher temperature to drive the solid-phase reaction and form a stable citrate-soluble silicon fertilizer structure. If the second calcination temperature is lower than or equal to the first calcination temperature, the silicate reconstruction and crystallization transformation cannot be completed, resulting in a significant reduction in product performance. If the second calcination temperature is too low, the reaction will be incomplete, and the product will contain free harmful substances; if the second calcination temperature is too high, it will lead to over-sintering, resulting in the loss of the silicon fertilizer's effectiveness.

[0054] In some embodiments, the acidic extract includes, but is not limited to, sulfuric acid solution or hydrochloric acid.

[0055] In some embodiments, the concentration of the acidic extract is 10 wt% to 20 wt%. As an example, the concentration of the acidic extract can be 10 wt%, 11 wt%, 12 wt%, 13 wt%, 15 wt%, 17 wt%, 18 wt%, and 20 wt%, etc.

[0056] In some embodiments, the target pH value is 1.2 to 1.9. As examples, the target pH value can be 1.2, 1.3, 1.5, 1.8, and 1.9, etc.

[0057] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments. The embodiments of this application are only examples, and all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0058] In Example 1, coal gangue was successively crushed and ground to obtain coal gangue powder with a particle size of 0.3 mm. The coal gangue powder was calcined at 700°C for 1 hour in air to obtain calcined coal gangue. 2 mL of 10 wt% nitric acid solution was added to 10 g of calcined coal gangue, and the mixture was stirred at 25°C for 2 hours for oxidation treatment. After the oxidation treatment, the resulting suspension was filtered, and the resulting filter cake was washed with water until the pH was neutral. Then, it was placed in a forced-air drying oven and dried at 105°C for 15 hours to obtain a precipitate. 3 g of sodium carbonate and 100 mL of deionized water were added to the precipitate and mixed. Then, the mixture was placed in a microwave reactor and microwave heat-treated for 20 minutes at a power of 500W, a temperature of 60℃, and a stirring speed of 500r / min. After microwave heat treatment, the resulting suspension was centrifuged at 2000rpm for 8 minutes to obtain filter residue and filtrate. The filter residue was calcined at 800℃ for 3 hours to obtain silicon fertilizer. 10wt% sulfuric acid solution was added dropwise to the filtrate until the pH reached 1.5. The resulting product was then placed in a separatory funnel for solid-liquid separation. The resulting precipitate was dried in a forced-air drying oven at 105℃ for 10 hours to obtain humic acid.

[0059] The silicon fertilizer prepared in Example 1 was tested, and the effective silicon (silicon that plants can absorb) content was 9862.24 mg / kg.

[0060] The yield of humic acid in Example 1 was found to be 4.12%.

[0061] In Example 2, coal gangue was successively crushed and ground to obtain coal gangue powder with a particle size of 0.074 mm; the coal gangue powder was calcined at 600°C for 1 hour in air atmosphere to obtain calcined coal gangue; 5 g of calcined coal gangue was added to 10 g of calcined coal gangue. A 15wt% nitric acid solution was stirred at 25℃ for 2 hours to induce oxidation. After oxidation, the resulting suspension was filtered, and the filter cake was washed with water until the pH was neutral. Then, it was dried in a forced-air drying oven at 105℃ for 15 hours to obtain a precipitate. 3g of calcium carbonate and 100mL of deionized water were added to the precipitate and mixed. The mixture was then placed in a microwave reactor and microwave heat-treated for 30 minutes at 800W power, 70℃ temperature, and 500r / min stirring speed. After microwave heat treatment, the resulting suspension was centrifuged at 2000rpm for 8 minutes to obtain a filter residue and a filtrate. The filter residue was calcined at 1000℃ for 3 hours to obtain silicon fertilizer. 10wt% hydrochloric acid was added dropwise to the filtrate until the pH was 1.5. The resulting product was then separated into solid and liquid components in a separatory funnel. The resulting precipitate was dried in a forced-air drying oven at 105℃ for 10 hours to obtain humic acid.

[0062] The silicon fertilizer prepared in Example 2 was tested, and the effective silicon content was 20914.87 mg / kg.

[0063] The yield of humic acid in Example 2 was found to be 6.24%.

[0064] In Example 3, coal gangue was successively crushed and ground to obtain coal gangue powder with a particle size of 0.1 mm. The coal gangue powder was calcined at 700°C for 0.5 h in air atmosphere to obtain calcined coal gangue. 4 mL of 10 wt% nitric acid solution was added to 10 g of calcined coal gangue, and the mixture was stirred at 25°C for 2 h for oxidation treatment. After the oxidation treatment, the resulting suspension was filtered, and the resulting filter cake was washed with water until the pH was neutral. Then, it was placed in a forced-air drying oven and dried at 105°C for 15 h to obtain a precipitate. 2 g of calcium chloride, 2 g of magnesium chloride, and 100 mL of deionization solution were added to the precipitate. The mixture was mixed with water and then placed in a microwave reactor. Microwave heat treatment was performed for 30 minutes at a power of 700W, a temperature of 80℃, and a stirring speed of 600 r / min. After microwave heat treatment, the resulting suspension was centrifuged at 2000 rpm for 8 minutes to obtain filter residue and filtrate. The filter residue was calcined at 900℃ for 3 hours to obtain silicon fertilizer. 15 wt% hydrochloric acid was added dropwise to the filtrate until the pH reached 1.5. The resulting product was then placed in a separatory funnel for solid-liquid separation. The precipitate was dried in a forced-air drying oven at 105℃ for 10 hours to obtain humic acid.

[0065] The silicon fertilizer prepared in Example 3 was tested, and the effective silicon content was 15954.87 mg / kg.

[0066] The yield of humic acid in Example 3 was found to be 4.10%.

[0067] In Example 4, coal gangue was successively crushed and ground to obtain coal gangue powder with a particle size of 0.3 mm. The coal gangue powder was calcined at 800°C for 1 hour in air to obtain calcined coal gangue. 4 mL of 20 wt% nitric acid solution was added to 10 g of calcined coal gangue, and the mixture was stirred at 25°C for 2 hours for oxidation treatment. After the oxidation treatment, the resulting suspension was filtered, and the resulting filter cake was washed with water until the pH was neutral. Then, it was placed in a forced-air drying oven and dried at 105°C for 15 hours to obtain a precipitate. 8 g of magnesium sulfate and 100 mL of deionized water were added to the precipitate and mixed. Then, the mixture was placed in a microwave reactor and microwave heat-treated for 30 minutes at a power of 400W, a temperature of 50℃, and a stirring speed of 500r / min. After microwave heat treatment, the resulting suspension was centrifuged at 2000rpm for 8 minutes to obtain filter residue and filtrate. The filter residue was calcined at 1000℃ for 3 hours to obtain silicon fertilizer. 20wt% sulfuric acid solution was added dropwise to the filtrate until the pH reached 1.5. The resulting product was then placed in a separatory funnel for solid-liquid separation. The resulting precipitate was dried in a forced-air drying oven at 105℃ for 10 hours to obtain humic acid.

[0068] The silicon fertilizer prepared in Example 4 was tested, and the effective silicon content was 8751.68 mg / kg.

[0069] The yield of humic acid in Example 4 was found to be 3.94%.

[0070] In Comparative Example 1, coal gangue was successively crushed and ground to obtain coal gangue powder with a particle size of 0.1 mm. 4 mL of 10 wt% nitric acid solution was added to 10 g of the ground coal gangue, and the mixture was stirred at 25 °C for 2 h for oxidation treatment. After oxidation treatment, the resulting suspension was filtered, and the resulting filter cake was washed with water until the pH was neutral. It was then placed in a forced-air drying oven and dried at 105 °C for 15 h to obtain a precipitate. 2 g of calcium chloride, 2 g of magnesium chloride, and 100 mL of deionized water were added to the precipitate and mixed. The mixture was then stirred in a magnetic stirrer for 30 min. After treatment, the resulting suspension was centrifuged at 2000 rpm for 8 min to obtain filter residue and filtrate. 15 wt% hydrochloric acid was added dropwise to the filtrate until the pH reached 2. The resulting product was then placed in a separatory funnel for solid-liquid separation. The resulting precipitate was placed in a forced-air drying oven and dried at 105 °C for 10 h to obtain humic acid.

[0071] The effective silicon content of the filter residue obtained in Comparative Example 1 was tested and found to be 864.52 mg / kg.

[0072] The yield of humic acid in Comparative Example 1 was found to be 2.41%.

[0073] Although preferred embodiments of the invention have been shown and described, it is conceivable that those skilled in the art can devise various modifications to the invention within the spirit and scope of the appended claims.

Claims

1. A processing method for coal gangue, characterized in that, Includes the following steps: Coal gangue is sequentially crushed and ground to obtain coal gangue powder; the coal gangue powder is then subjected to a first calcination to obtain calcined coal gangue; the calcined coal gangue is mixed with nitric acid solution and subjected to oxidation treatment to obtain a precipitate; the precipitate, a chemical activator, and a solvent are mixed and subjected to heat treatment, followed by solid-liquid separation to obtain filter residue and filtrate; the filter residue is then subjected to a second calcination to obtain silicon fertilizer; an acidic extract is added to the filtrate to adjust the pH value to acidic to obtain humic acid.

2. The coal gangue processing method according to claim 1, characterized in that, The particle size of the coal gangue powder is 0.074~0.3mm.

3. The coal gangue processing method according to claim 1, characterized in that, The first calcination temperature is 600~800℃, and the first calcination time is 0.5~1.5h; the first calcination is carried out under aerobic conditions.

4. The coal gangue processing method according to claim 1, characterized in that, The ratio of the calcined coal gangue to the nitric acid solution is (2~8) g: 1 mL; the concentration of the nitric acid solution is 5wt%~20wt%.

5. The coal gangue processing method according to claim 1, characterized in that, The oxidation treatment temperature is 10~30℃, and the oxidation treatment time is 1~4h.

6. The coal gangue processing method according to claim 1, characterized in that, The mass ratio of the calcined coal gangue to the chemical activator is 1~10:1; the ratio of the amount of the chemical activator to the amount of the solvent is 1g:(5~35)mL.

7. The coal gangue processing method according to claim 1, characterized in that, The chemical activator includes one or two of nitrates, sulfates, carbonates, and chlorides; the nitrate includes at least one of calcium nitrate, magnesium nitrate, and potassium nitrate; the sulfate includes at least one of calcium sulfate, magnesium sulfate, and potassium sulfate; the carbonate includes at least one of calcium carbonate, magnesium carbonate, and potassium carbonate; the chloride includes at least one of calcium chloride, magnesium chloride, and potassium chloride; and the solvent includes water.

8. The coal gangue processing method according to claim 1, characterized in that, The heat treatment includes microwave heat treatment; the conditions for microwave heat treatment are: power of 200~900W, temperature of 30~90℃, and time of 20~60min.

9. The coal gangue processing method according to claim 1, characterized in that, The second calcination temperature is 700~1100℃ and is higher than the first calcination temperature, and the second calcination time is 2~6h.

10. The coal gangue processing method according to claim 1, characterized in that, The acidic extract includes a sulfuric acid solution or hydrochloric acid; the concentration of the acidic extract is 10wt%~20wt%; and the target pH value is 1.2~1.9.